1. Field of the Invention
The present invention relates to an anti-vandalism layer. In particular, the present invention relates to an anti-vandalism layer for vehicle seats, vehicle roofs, vehicle tarpaulins, tents, inflatable structures, wall facing, and similar objects having an incisible exterior layer and subject to vandalism.
2. Description of the Related Art
Particularly in public transportation vehicles such as trains, busses, and the like, vandalism in the form of damage to seat coverings, especially by ripping the coverings to shreds, is ever on the rise. For this reason, operators of public transportation are increasingly forced to guard against this vandalism when outfitting new vehicles or when replacing damaged seats. The interest in cut-resistant seat fabrics has therefore increased significantly from the recent past.
Not only vehicle seats are endangered by vandalism, however. Increasing vandalism, often coupled with the intent to steal, has also been observed on sliding vehicle roofs and convertible tops; tarpaulins on trucks or other commercial transport vehicles; tents, inflatable structures, and other objects in textile construction; and wall facing such as impact pads in sports facilities or public transportation.
In order to prevent or at least hamper vandalism, several different solutions to the problem have been proposed.
For example, DE-A 3 702 639 suggests the use of a fine-mesh metal woven fabric between the exterior material of the seat covering and the foam serving as the body of the seat. A similar approach is proposed in GB-A 2 204 235.
Knit structures made from wire or metal fibers are described in DE-U 90 04 625 and EP-A 190 064. A protective layer made from metal rings is described by DE-A 3 711 419.
Flat structures made from metal wires or metal fibers have serious disadvantages for vandalism protection, however, especially in the case of vehicle seats. These disadvantages are seen during seat manufacture and particularly when the seat is used. These anti-vandalism layers are normally located under the seat covering itself, since only here can they exercise their protective action without attracting the attention of the occupant or the vandal.
Such metal-wire or metal-fiber flat structures are relatively difficult to work due to their limited flexibility, since additional cutting or scissoring steps are needed especially to cover uneven surfaces, something required to a great extent in the manufacture of vehicle seats and exerting a negative effect on production costs.
The disadvantages of metal-wire or metal-fiber anti-vandalism layers are especially noticeable when the seat is in use. Such anti-vandalism layers considerably impair sitting comfort because the inserts result in a harder and thus less comfortable sitting surface.
Moreover, the repeated separation of individual broken wires during use represents a significant problem. These wires pierce the actual seat covering and project from the surface in a way that their presence is often not apparent. This can result in injuries with very serious consequences to users of public transportation. When metal-wire or metal-fiber anti-vandalism layers are employed, operators of public transportation even speak of an increased risk of AIDS infection. For this reason, public transportation operators have a great interest in replacing these anti-vandalism layers with more suitable materials.
For this reason, anti-vandalism layers made from cut-resistant textile fibers have also been described. For example, AU-A 86-52 272 proposes constructing the anti-vandalism layer from a woven fabric or a needle felt made from aramid fibers and gluing this layer to the exterior material. EP-A 355 879 also mentions a needle felt made from aramid fibers as an anti-vandalism layer. FR-A 2 573 969 merely cites aramid fibers, without any information as to what types of flat structures are involved.
Neither woven fabrics nor needle felts made from aramid fibers, however, exhibit the required cut and puncture resistance in corresponding trials. While these approaches avoid the disadvantages of metal anti-vandalism layers, they do not sufficiently meet the requirements for anti-vandalism layers with respect to cut and puncture resistance.
Two anti-vandalism layers, one made from a metal screen and a second from aramid fibers, are described in FR-A 2 592 334. In this case, the aforementioned disadvantages are somewhat reduced, but there is still the risk of injury due to protruding wires, and the disadvantage that metal anti-vandalism layers cannot be as readily worked. Furthermore, this approach results in higher production costs than for a uniform anti-vandalism layer.
A protective layer, which can comprise various flat structures and a wide variety of materials such as glass-, polyester-, ceramic- , aramid-, or carbon fibers is mentioned in EP-A 512 382. These fiber materials can take the form of screens, nets, woven fabrics, or knits. This patent application, however, does not teach how such a protective layer would be constructed in order to adequately resist vandalism.
A protective layer in the form of a knit structure is described in DE-A 42 08 600. The fiber material is preferably a blend of preoxidized polyacrylonitrile fibers and aramid fibers. Since this knit construction results in too many rigid connections such as drawn warp and weft threads, the cut resistance of such a protective layers is inadequate. Although the aforementioned approaches describe special protective layers located under the actual seating layer, DE-C 37 11 837 concerns itself with the design of a seat covering with vandalism-impeding characteristics. Here, a fabric is proposed in which a portion of the warp and weft threads are made from stranded wire with a sheath of laced textile yarn. The sheath can apparently be moved with respect to the core. Such a construction does not meet the requirements for a vandalism-inhibiting material, since it fails to offer sufficient protection against incision with a knife, due to the inflexible wires. Moreover, the ability to work a covering material is impaired by the stranded wire. Finally, such a seat covering can be manufactured only at high cost.
DE-C 35 45 071 proposes a fire-protection layer made from elastic material, treated for flame retardation, in conjunction with a wire, and this layer can simultaneously protect against cutting. Here, a wire is incorporated in a woven or knit fabric, but there is no teaching concerning the type of wire, the construction of the flat structure, or the fiber material. The inclusion of wire is in itself not sufficient to provide adequate cut resistance and in particular to avoid the risk of injury caused by the wire. Since the proposed companion fibers are elastic yarns made from any type of raw material, the required cut resistance is not attainable with such an anti-vandalism layer embodiment. Furthermore, in the anti-vandalism layer proposed in this case, as well as in other proposals involving wire, protrusion of the wire cannot be adequately prevented. Additional disadvantages of the fire-protection layer proposed here are the insufficient cut resistance resulting from the described short laps and the proposed rigid attachment to the exterior material, as well as the inadequate flexibility offered by the proposed stationary thread technique. The varied requirements for an anti-vandalism layer cannot be met with the described construction.
While numerous products have been proposed for reducing damage to public-transportation vehicle seats by vandalism, the problem of vandalism, usually coupled with the intent to steal, has received little attention in the case of other products such as tarpaulins for trucks, tents, and the like. A textile fabric impeding vandalism and especially developed for use in truck tarpaulins, tents, inflatable structures, and the like, is described in German patent application P 43 40 483.9.
An anti-vandalism flat structure especially suited for convertible tops but also for other objects subject to vandalism is proposed by DE-A 42 15 662. It consists of a composite material comprising at least two layers, of which at least one comprises yarns made from aramid fibers, that can apparently be pushed together using little force.
Likewise, a material for foldable vehicle tops with an exterior material made from a coated polyester woven fabric and a reinforcement layer in the form of a woven screen fabric or thread composite made from glass-, carbon-, or metal fibers, for example, is described in DE-U 92 06 365.
Finally, DE-U 92 17 352 describes a bellows with a cut-resistant insert layer of metal wires or high-strength synthetic fibers.
All of the previously cited approaches have considerable drawbacks with respect to workability, risk of injury, and manufacturing costs. For the most part, they also do not offer the desired cut resistance for sufficient protection against vandalism.